1. Field of the Invention
The present invention relates to a code refreshing display control device for displaying character information on various displays such as a raster scanning CRT display and a liquid crystal, etc.
2. Description of the Prior Art
Referring to FIG. 2, the construction of a character display system of a prior code refreshing display control device is illustrated in the form of a block diagram. In the figure, designated at 1 is a display address generator circuit for generating a display address in given display timing, 7 is a refresh memory into which character code information is written corresponding to a display position on a display screen and of which the same is read out following a character address from said display address generator circuit 1, 8 is a character generator in which a specific style character font is stored in a ROM or a RAM corresponding to a character code and which is to generate a corresponding character font by a character code read from the refresh memory 7, and 6 is a video control circuit into which output data from the character generator 8 is inputted for generating various video signals suitable for a display device.
Here will be described operation of the prior display control device. The display address generator circuit 1 generates in a predetermined period a character address as an address of the refresh memory 7 corresponding to a display screen, and a raster address of a character to the character generator 8. The refresh memory 7, in which a character code has previously been written corresponding to a display position on a display screen, and outputs as data a character code in an area addressed by the foregoing character address. The character code is inputted into the character generator 8 together with the foregoing raster address as a character address of a corresponding character font. The character generator 8 then outputs the character font as data. The video control circuit 6 converts the output data from the character generator 8 to a video signal for display, and supplies a signal suitable for the display device to the same. Hereby, the display device displays the character on its display screen.
The prior code refreshing display control device is constructed as described above, and generally incorporates a RAM as the refresh memory and a ROM or a RAM as the character generator, requiring physically a plurality of types of independent memories and hence a complicated control circuit for a plurality of memory accesses. Further, use of a plurality of types of memories makes difficult the realization of space saving of a parts packaging area, of cost reduction, lowering of troubles, and so on.